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<br />I <br />I <br />I <br />I <br /> <br />I <br /> <br />Option 6 - Flatten the Upstream Slope to 2.5IHI:1.0IVI and Armor against Wave Action <br />This option consists of placing a conventional upstream slope protection material <br />on the upstream slope of the dam. Due to concerns about the slope stability, the <br />upstream slope would be flattened to 2.5 (horizontal):1.0 (vertical) to enhance slope <br />stability. Included would be a combined cutoff wall and footing along the upstream toe <br />of the dam to support the slope protection material. The design concept for these <br />options are shown in Figure 9. <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />Option 6A : Armor with New Concrete Slabs <br />In this option, it is proposed to remove the existing concrete slab facing to <br />expose the embankment soils, allowing observation and compaction of the surface prior <br />to placement of fill against the slope. The existing slabs would be disposed of in the <br />lakebed, positioned to provide incidental benefit as a brea~water. The toe cutoff wall <br />and foundation would be constructed of concrete. A granular filter layer would be <br />placed on the finished fill surface, and the concrete slabs constructed on the filter. <br />Specific design issues would include concrete design for performance in an adverse <br />environment, and sealing/filtering of slab joints to prevent embankment materials from <br />piping. Replacement slabs would be designed at a six to eight inch thickness. The dam <br />crest would be reconstructed to elevatibn' 41.0 instead of a parapet wall in order to <br />provide adequate freeboard for wave runup on the concrete slabs. <br /> <br />I <br /> <br />I <br />I <br /> <br />I <br /> <br />I <br /> <br />In this option, the issues of possible voids and/or loose soils under the existing <br />slabs, and the dam embankment stability issues are addressed, as contrasted to Options <br />2 and 3. Life span for the work is expected to be 50 years, and a new slab <br />replacement program, excepting the cutoff wall and foundation toe construction, would <br />be initiated around 2051. Potential problems with concrete slabs include limited ability <br />to deform with unusual dam embankment movement, and thin sections which when <br />cracked allow easy movement of water through the cracks. Soil movement through <br />slab joints and cracks is mitigated with the filter bedding placed on the slope under the <br />slabs. The expected long construction duration is expected to impact the ability to use <br />and/or store water. <br /> <br />I <br /> <br />I <br />I <br />I <br />I I <br />I <br /> <br />31 <br />